WATER SUPPLY OF PLANTS VIEWED FROM THE STANDPOINT OF THE BIOENERGY APPROACH

The most promising of the previously known approaches in the use of theories in the practice of water supply of plants is the approach based on the bioenergy theory of productivity. The paper contains a brief review of conventional approaches to the use of theories and discoveries in the practice of water supply of plants and methods of its evaluation. It is proposed to estimate the need of plants for water by the amount that should be spent on transpiration to reduce the plant leaf temperature to the optimum temperature for photosynthesis by evaporative cooling. It is shown that optical radiation, along with photosynthetic radiation, has other effects on plants (thermal, photoperiodic, photomorphogenic, etc.). The authors suggest identifying the transferability of indicators (criteria) describing the basic conditions of the external environment on thermodynamic basis. Thus, the research purpose is to justify the analytical dependence to take into account the influence of these factors on the water supply of plants. With the help of experimental measurements and calculations of evaporated water, two samples of water lost in evaporative cooling are obtained, which have the same characteristics. On the basis of the carried out researches, the analytical dependence of evaporated water at constant illumination is obtained in the form of a polynomial of the second degree. It is shown that when lighting is switched on, the evaporated water first decreases, and then the phase of active photosynthesis occurs, and the amount of evaporated water grows. It has been found that taking account of bioenergetic aspects, the plant should be provided with water at an average rate of 0.7 g/h, and with the onset of the active phase of photosynthesis, an hourly amendment should be made according to the obtained dependence.

在现有植物供水实践的理论应用方法中，最具应用前景的是基于生产力生物能理论（bioenergy theory of productivity）的研究路径。本文对植物供水实践中理论与发现的传统应用方式，及其效果评估手段开展了简要综述。研究提出，可通过将植物叶片温度通过蒸发冷却降至光合作用最优温度所需的蒸腾作用（transpiration）耗水量，来估算植物的需水总量。已有研究证实，光辐射（optical radiation）与光合辐射（photosynthetic radiation）共同作用时，会对植物产生多类额外效应，包括热效应、光周期效应、光形态建成效应等。作者建议基于热力学（thermodynamics）基础，对描述外部环境基本条件的指标（评判准则）的可迁移性进行识别与验证。据此，本研究的核心目标在于构建可表征上述多因素对植物供水影响的解析关系式。通过对蒸发水量的实验测量与数值计算，得到了两组蒸发冷却耗水样本，二者具备完全一致的特性参数。基于本次研究工作，我们推导出恒定光照条件下蒸发水量的解析关系式，其形式为二次多项式（polynomial of the second degree）。实验结果表明，当光照开启后，蒸发水量会先出现阶段性下降，随后进入活跃光合作用阶段，此时蒸发水量将逐步升高。研究发现，若纳入生物能学维度考量，植物的平均供水速率应为0.7克/小时；当进入活跃光合作用阶段后，则需依据所得到的解析关系式进行每小时的供水修正量调整。